Paper felt



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PAPER FELT.

naraeee.

Ito Drawing.

To all whom it may concern.

Be it known that l, ALBERT L. CnArr, a citizen of the United States, residing at Marblehead, in the county of Essex and State of Massachusetts, have invented new and useful Improvements in Paper Felt, of which the following is a specification.

This invention has for its object to provide an inexpensive strong pliable free and porous paper felt such as can be' impregnated with bituminous compounds in the manufacture of roofing or flooring materials. Such felt must be open or ,free and highl porous or absorbent, so that it will rapi y absorb such materials as molten asphalt or other relatively heavy and adhesive bituminous compounds. Moreover it must possess considerable strength to withstand the tensile strains to which it is sub jected in the saturating and impregnating operations, and it must be pliable, without cracking or brea when bent.

To produce such paper felt, ll employ a mixture of rags, news or waste paper, Qaft or sulfite pulp and sawdust.

In practice, I charge a beating engine with hot water, preferably'at a temperature of 200 to 212 lE"., and then add about twenty partsby weight of waste paper such as news print. The beater roll is lifted from the bed plate and is set in rotation, until the paper is disintegrated. Then ll add about thirty parts by 'wei ht of rags and about twenty parts by weig t of such chemical wood pulp as sulfite, sulfite screenings, sulfate, or sulfate screenings, preferably sulfate or sulfate screenings. The beater roll is adjusted to the bed plate, and the beating is continued for about twenty minutes. During this operation, about thirty parts by weight of fine sawdust are gradually added to the beater stock. After the stock is thus mixed, it is then ready tobe further thinned .with water and formed into a web or sheet b any suit- Specification of Letters Patent.

- ity in thickness or caliper.

Patented Mar. 22, 19211.

Application filed November 17, 1919. Serial No. $38,265..

that of four heaters in which rags alone are used to make the sheet, and further that, the weights of dry stock and the caliper 'of the finished sheets being equal, the yardage of finished sheet material produced by the stock herein described is much greater than that vproduced by stock consisting of rag stock alone. I regard the use of sawdust as important inasmuch as it assists in inakingthe sheet free, open and porous, increases the caliper,and in addition provides a smoother surface on the sheet and a greater uniformllhe cliemical wood pulp, '5. 6., sulfite,-sulfate or screenings, increases the strength of the sheet.

The waste paper gives body to'the sheet,

but, as it tends to harden .or stifienand close the sheet, a great proportion thereof should not be employed. llts advantage is cheapness, and, if this is not a consideration, it maybe replaced by an equivalent proportio of rags.

he function of the rag'fibers is to assist in the felting of the sheet, or the binding of the component fibers thereof together, and to insure the flexibility or pliability of the sheet. A sheet as herein described has decided advantages over one which is pro-,.

duced from rags alone, in addition to those hereinbefore pointed out. That is, in addition to being longer and thicker, it is more porous, and flexible or pliable, and of greater strength. For'example, a sheet of paper felt made entirely of rags and having a weight of 42 pounds has a caliper of about 40 and a Mullin-test of about 30. A felted sheet as herein described having a wei ht of 42, has a caliper'of about 4:8 and a ullinprising in addition to the rags, paper and sawdust alone, has a greater caliper than t0 and a lower Mullin-test than a sheet made at rags alone, say, about 20 to 25. On the test of about 45. Obviously, a sheet comchemical wood pulpin the sheet embodying the present invention is to increase the stren g'th of the sheet without decreasing itsporoslty,

flexibility and caliper. A sheet embodying the invention, therefore is better adapted for use in the manufacture of roofing and flooring material. It maybe passed more rapidly through the saturating I tank, in which the molten asphalt or bitumithose 'equi'va entstherefor', as constituting a de-. parture from the. hereindisclosed invention,

' so long assubstantiall secured as herein set nous compound is contained, and more effectively saturated or impregnated with such compound, as a result of which shingles or shingle stripsproduced therefrom are less likely to curl or buckle when exposed to the elements.

Afterbeing thus saturated with a relatively low-melting-point" bituminous compound, the sheet is rinted for flooring purposes, or, if, desire ,is coated with a highmelting-point asphalt or bituminous com-. pound, and may be surfaced with crushed slate or other equivalent mineral. Shingles or shingle strips may be cut from-the finished' sheet. In lieu of impregnating thedry felt sheet, the asphaltl'c material, in the'form of a nonadheslve emulsion, may be added to the stock prior-toits being formed into a web, this step however being herein disclaimed, as per se it constitutes nopart invention. 110 I have herein ofm sheet, I should not regard deviations from. roportions on the substitution of fy the e results are th? I v i aper ' dition to rag described what Iv regard asthe best proportions of the several ingredients used in the manufacture of'the 'Jdurin such heating grad a the mixture, and finally forming assaeso prepared roofing, allas claimed in my application Serial No. 215,891, filed February What I claim is: 1 I 1. An open porous flexible smooth-surfaced sheet of gaper felt comprising in adber, finely divided sawdust for increasmg the. caliper and providing a smooth open porous surface, and a sufficient proportion of chemical wood pulp to offset the decrease in strengthcaused by the presence ofsawdust, all producing asheet of.

greater caliper and yardage and not less in strength than one reduced by an equivalent weight of rag ber.

2. An open porous flexible sheet of paper.

- felt, conslsting of rag fiber, wastepaper,

chemical wood pulp and sawdust.

.3. An open porous flexible sheet of pa er felt, consisting of approximately, by weig t,

thirty parts 01f rags, twenty parts of waste paper, twenty parts of chemical wood pulp and thirty parts of sawdustLf v4:. The herein'described process of mak- I ing paper felt, which consists in first disintegratin .waste aper in water, heating 'therewit ragsan chemical-wood ulp, add- .ing sawdust-to the mixture, an forming such'mixtureinto a web. i 5. .The herein des'e 'bed process of mak- .ing'paper felt, which consists in' disinte grating-waste. mg rags and c emical wood gulp therewith, yadding .fine sawdus't'to v such mixtureiiito a? Web or sheet."

aper inlhot'water, then beat- In s ny. whereof I have afi d 

